Ultrashort optical pulses are useful in a variety of applications, including materials processing such as micromachining, ophthalmology, biomedical imaging, ultrafast spectroscopy, ultra-high-speed optical networks, reaction triggering, etc. Energetic optical pulses of sub-picosecond and femtosecond (fs) duration may be produced by sending seed optical pulses from a lower-power optical source, such as a mode-locked laser, through an optically pumped broad-band power amplifier. However, short pulses that propagate through such amplifiers may experience amplitude and/or phase degradation, such as gain narrowing and self-phase modulation, resulting in an undesired broadening of an output pulse. The pulse shape degradation in optical amplifiers may be at least partially overcome by ultrafast active pulse shaping techniques developed earlier for telecommunication applications, such as for example temporal pulse shaping using acousto-optic modulators or spectral pulse shaping using liquid crystal spatial light modulators. Implementing active pulse shaping techniques for multi-pass and regenerative optical amplifiers based on Ti:Saphire gain elements, which optical gain bandwidth may be as high as 200-300 nanometers (nm), resulted in optical sources of 3-20 fs pulses geared for scientific research applications. However, the active pulse shaping may require the use of fast optical modulators and complicated control and feedback loops, thereby considerably complicating the amplifier design and raising cost. Another technique for pulse shaping in Ti:sapphire amplifiers relies on the use of an intra-cavity shallow broad-band filter inserted within the multi-pass cavity of the amplifier. This technique may not be, however, directly applicable to single-pass optical amplifiers that are based on gain elements that have a much higher peak gain value but a narrower gain bandwidth than the Ti:sapphire material, such as for example single-crystal Yb:YAG rods or disks. Optical pulse sources based on such gain elements with 10 dB of gain or more per pass that may be capable of generating somewhat longer sub-picosecond pulses of 400-800 fs duration are of interest for industrial application, and may benefit from an inexpensive pulse shaper to combat the gain narrowing effect in the amplifier.
Accordingly, it may be understood that there may be significant problems and shortcomings associated with current solutions and technologies for providing sub-picosecond optical pulses in optical sources using high-gain narrow-bandwidth gain elements.